The present invention relates to a printing control system and, more particularly, to a printing control system facilitating interruption of the printing of a first job to permit a second job having a higher priority to be printed.
Much of the work product of data processing systems is intended for transformation to hard copy via a printer using digital imaging processes. A data processing system may be configured to feature a dedicated printer coupled to an individual personal computer. On the other hand, networked data processing systems have become prevalent in office settings where extensive document processing is performed. Typically, a local area network (LAN) or wider area network includes a plurality of linked workstations, file servers, terminals, scanners, printers, and other data processing devices. LANs provide a means for sharing resources, such as printers, among a number of users, each operating a dedicated workstation. Sharing printers over a network reduces the number of printers required, permits a more sophisticated printer to serve users than would otherwise be economically justified, and reduces the cost of maintaining the printing capability of an operation. A LAN manager is typically responsible for the integration of shared resource in a network and a LAN manager may include a printing control system and a plurality of print drivers utilizing a plurality of different page description languages (PDLs) to facilitate the operation of a plurality of networked printers.
In a typical printing operation with a data processing system, a user at a workstation selects one or more available printing options to be applied to the document and sends the document to a printing control system as a print job described by a Page Description Language (PDL). The printing control system places the jobs in an order and controls the input of data to the printer's engine to ensure that print jobs are correctly printed in a desired sequence. Network printing is further complicated by the fact that a print job can originate from any of the attached workstations at any time. Typically, the print control system accepts a print job from a workstation with options specified by a user, copies the print job and the options over a communications channel, orders the print jobs in a print queue, converts or filters the job to the printer's native language, and, following printing, performs clean up functions, such as notifying the user of the completion of the job.
The order in which jobs are printed is determined by prioritizing rules of the printing control system. Typically, print jobs are ordered according to the time that the request for printing is received by the control system (first in—first out or FIFO). However, print jobs may also be ordered according to the time required to print the job, for example, a shorter job might be printed first. The printing controller may also put print jobs requiring binding first or last in the print queue or may queue jobs as a function of the availability of the required print media in the printer.
Printing controllers may also permit a user to arbitrarily change the order of printing jobs in the print queue. A user with an urgent job may be able to move that job to the front of the queue so that the job will be printed immediately following the completion of the job in process. Typically, the user requesting printing can specify a relative printing priority as an option for the printing job or access a printer folder to manually reorder the print queue. The printing control system may also assign a higher priority to print jobs originating at certain networked workstations.
While printing controllers provide a number options for ordering and reordering print jobs, these options can only be applied at the boundary of a job. In other words, changing the order of jobs in the print queue does not effect a job being printed at the time of the change. For example, if a lengthy report with extensive graphics is currently being printed, the printing cannot be interrupted by an urgent print job and then restarted after the urgent job is completed. To interrupt a currently printing job, the job must be canceled causing the unprinted portion of the job to be removed from the system. After the urgent job has been printed, printing of the canceled job must be manually restarted for all or a user designated portion of the job. This procedure is particularly complicated and inconvenient with a data processing network where each print job may be controlled by a different individual and individual users may be widely separated.
What is desired, therefore, is a printing control system that permits a currently printing job to be interrupted for a more urgent job and then restarted.